Extraction-Chromogenic System for Silver(I) Based on Tetrazolium Violet and Semicarbazide Hydrochloride

• Published in: Russian journal of general chemistry 2019-10, Vol.89 (10), p.2136-2142
• Main Authors: Hristov, D. G., Divarova, V. V., Mancheva, R. D., Gavazov, K. B.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Chloroform; Ethylenediaminetetraacetic acid; Ethylenediaminetetraacetic acids; Reagents; Spectrophotometry
• ISSN: 1070-3632; 1608-3350
• DOI: 10.1134/S1070363219100232

In the presence of semicarbazide hydrochloride (SCH) and traces of Ag I , the tetrazolium salt 2,5-diphenyl-3-(1-naphmyl)-2 H -tetrazolium chloride (Tetrazolium violet, TV) is reduced in alkaline medium to intensely colored chloroform-extractable 3,5-diphenyl-1-(1-naphthyl)formazan (Tetrazolium violet formazan, TVF). The following experimental parameters have been examined for finding optimal conditions for color development and extraction-spectrophotometric determination of Ag I : concentration of reagents, extraction time, volume of the two phases, presence of dissolved oxygen, and light. Under the optimal conditions ( c TV = 4.0 × 10 −5 mol/dm 3 , c SCH = 2.4 × 10 −3 mol/dm 3 , c NaOH = 4 × 10 −1 mol/dm 3 , V aq.phase = 25 cm 3 , V chloroform = 4 cm 3 , extraction time t = 5 min) an isomer of TVF with λ max = 511–512 nm is predominantly extracted. The calibration curve (at 512 nm) is linear in the concentration range of 0.013–0.028 µg cm −3 of Ag I . The following ions do not interfere in determination of 0.65 µg of Ag I ; Li + , Na + , K + , N H 4 + , H 2 P O 4 − , F−, Cl−, S O 4 2 − , B 4 O 7 2 − , R e O 4 − , tartrate, and citrate (5000-fold excess); Mg II and EDTA (1000-fold excess); Pb II and Ba II (500-fold excess); Al III (300-fold excess); Zn II and Ca II (100-fold excess); V V (50-fold excess); Hg II , Hg I , Mo VI and Fe III (25-fold excess); and Cu II and W VI (10-fold excess). Cr III interferes in the process at a mass ratio of 1 : 1, however small amount of this cation (1.5-fold excess) can be masked by EDTA.